THE ACTIONS OF SUCCINYLCHOLINE ON THE MAMMALIAN MOTOR NERVE TERMINAL

¹ Department of Pharmacology, Cornell University Medical College, New York, New York

Succinycholine (Sch), which is usually assumed to act exclusively on the postjunetional structures of time neuromuscular junction, profoundly affects the motor nerve terminal. It attenuates posttetanic neural repetitive activity, causes time neural response to a single stimulus to become repetitive, and initiates in time motor nerve action potentials which are independent of an external stimulus. These effects are produced by a wide range of Sch doses, including those well below threshold for blockade of neuromuscular transmission. Provided time dose is kept below the transmission blocking dose, these neural events are fully reflected in muscle electrical and mechanical activity. The fact that Sch affects the motor nerve termninal in much smaller and much larger doses than those which a affect neuromuscular transmission and that, qualitatively, some of these effects are capable of causing trainsmission block suggests that the motor nerve terminal is the primary site of Sch action.